What is a TCO film?

In thin film silicon solar cells,*1 TCO films function as conductors (electrodes) that derive electrical energy from sunlight. These films must meet the following conditions: they must be able to conduct electricity, they must be transparent, and they must be able to efficiently scatter light by means of their surface concavoconvex texture, to conduct more light into the photovoltaic layer for higher power generation efficiency.

Crystal silicon solar cells and thin film silicon solar cells

*1 Thin-film silicon solar cells are made by forming very thin silicon films on glass substrates. These cells use only about one-hundredth the amount of silicon compared with typical crystalline silicon solar cells (solar cells made by processing silicon ingots into wafers). On the other hand, thin-film silicon solar cells have lower power generation efficiency (less than 10%) compared with crystalline silicon cells (approx. 15%) , which is the challenge for thin-film silicon solar cells.

Thin-film silicon type

Features of the AGC Group's technology

The AGC Group's TCO films have the following characteristics: they are highly conductive films with low electric resistance and scatter light very efficiently. We embarked on the development of TCO films in 1985. Our first product, Type U TCO film became the world's standard for TCO films, but it scattered only 10% of incoming sunlight (haze rate). After releasing the Type VU TCO film, which had a better haze rate, on the market, we unveiled the development of Type HU TCO film, which can scatter up to 90% of incoming sunlight through our original nano-scale (one-billionth of a meter) film forming technology. By generating smaller concavoconvex parts onto the existing concavoconvex surface, we have made it possible for the film to reflect sunlight in a more complex manner in order to conduct more light into the photovoltaic layer for improving the power generation efficiency.
The AGC Group also possesses a technology to coat TCO films onto float glass concurrently at the time the glass is produced. We will continue our development activities to meet the needs of still more customers.